The production, processing, storage, transportation, as well as unintentional spillage of crude oil and petroleum distillates has contributed to the release of hydrocarbon into the environment. This has resulted in large number of polluted sites and enormous volumetric quantities of soil, which have been contaminated with hazardous substances. Soil contamination can cause extensive damage to the local ecosystem by accumulating in the tissue of animals and plants and by causing death thereto and/or mutation to the progeny thereof. Such contamination can also present a serious health threat to humans, and, in extreme cases, can render the contaminated area unsuitable for human habitation.
The hydrocarbon-contaminated soil/storage pits are generally treated by secure landfill, incineration, indirect thermal treatment, aeration, venting, air sparging and conventional bioremediation. Sludge stored in storage pits and oil contaminated soil having large amount of stones/gravels/coarse material and free flowing water cannot be treated by these methods. In these areas the hydrocarbon oil present in sediment does not remain bio-available for microbial action and oil remain partitioned between water phase and solid soil/gravel particles.
There are many hydrocarbon-contaminated sites like near the riversides, low-lying areas, in the rain prone areas where hydrocarbon contaminated soil remain in the slurry form and water remains in free flowing conditions on the surface. These sites cannot be treated by conventional methods. The problem becomes much pronounced when such water-flooded hydrocarbon contaminated area contains large gravels and stones besides soil.
To have a successful treatment of oil-contaminated soil the release of hydrocarbon adsorbed on solid soil particles/gravel surface is essentially required. Various surfactants of chemical or biological origin are having ability to release oil from sediments. However, chemical surfactants owing to their toxicity towards microorganisms, particularly hydrocarbon degrading microbes and other adverse ecological impact are not used commonly and moreover, chemical surfactants are found less effective for sustained release of oil. Improved hydrocarbon release and degradation by addition of purified biosurfactant is reported in prior art (Rahman et al., Bioresource. Technology, 90, 159-168. 2003; Kuyukina et al., Environment International., 31,155-161, 2005). However, for field bioremediation application based on bioaugmentation, addition of the biosurfactant-producing bacteria may be beneficial and more practical than exogenously adding purified biosurfactant.
Dean and co-workers (Journal of Environmental Quality 30:1126-1133 (2001)) studied phenanthrene biodegradation by co-culture of phenanthrene degrading bacteria and bacteria having surfactant-producing strains in Fallsington sandy loam soil microcosms and aqueous medium, separately. The co-culture of contaminant-degrading and surfactant-producing bacteria resulted in the overall enhancement of phenanthrene degradation.
Van Hamme and Ward, (Appl Environ Microbiol. October; 67(10):4874-9, 2001.) studied the physical and metabolic interactions between Rhodococcus sp. strain F9-D79 and Pseudomonas sp. strain JA5-B45 were examined during growth on Bow River crude oil in 250-ml Erlemneyer flasks containing 50 ml of medium and reported a slight enhancement in TPH removal by the coculture than the individual bacterium. In the co-culture Rhodococcus sp. strain F9-D79 forms excellent, though transient, crude oil-water emulsions between 24 and 48 h of incubation. Pseudonmonas sp. strain JA5-B45 does not emulsify oil but does efficiently degrade crude oil.
U.S. Pat. No. 3,871,956 features a method for cleaning accidental oil spills on water or in soil. The method of this patent does not utilize temperature or oxygen controls and is not a self-perpetuating process.
U.S. Pat. No. 5,035,537, discloses a method for treatment of soil, porous rock and similar material contaminated by petroleum, hydrocarbon and volatile organic compounds and includes the steps of gathering the contaminated soil, disbursing it uniformly on an impervious horizontal surface to a depth of four to six inches, treating it with an emulsifying agent and allowing the emulsifying agent to seep through the soil and volatilize the hydrocarbon and organic compounds in the soil.
U.S. Pat. No. 5,055,196 discloses a process for treating soil or sludge to remove contaminants in contact with the soil or sludge. More particularly, this method relates to a process in which inorganic contaminants, such as metal or metal salts, or organic contaminants, such as PCBs, are removed from water-wet soil and sludge.
U.S. Pat. No. 5,059,252 discloses a method for on-site bioremediation of soils contaminated with petroleum derived hazardous wastes. This method for enhancing bioremediation includes the step of applying a cationic ion exchange resin to the contaminated soil in an amount sufficient to promote growth of organisms capable of degrading the hazardous waste.
U.S. Pat. No. 5,427,944 teaches a process for biodegrading polycyclic aromatic hydrocarbon contaminants using a mixed bacteria culture of Achromobacter sp. and Mycobacterium sp. and nutrient. The mixed bacteria culture was utilized for in situ or ex situ bioremediation of contaminated soil, or in any of various conventional bioreactors to treat contaminated liquids such as landfill leachates, groundwater or industrial effluents.
U.S. Pat. No. 5,453,133 relates to a process for removing contaminants, such as hydrocarbons, from soil. The process involves contacting the contaminated soil with a suitable solvent for the contaminant, in the presence of a bridging liquid, which is immiscible with the solvent, while agitating. The amount of the bridging liquid and the degree of agitation are balanced to control the particle size of the substantially contaminant-and solvent-free soil agglomerates so formed.
U.S. Pat. No. 5,494,580 relates to a method for decontamination of a hydrocarbon-polluted environment by the use of certain bacterial compositions.
U.S. Pat. No. 6,057,147 discloses an apparatus and method for enhanced bioremediation of hydrocarbons removed from a contaminated object. The device and method promote continuous microbial bioremediation of hydrocarbon contaminants in a self-propagating manner while cleaning the solution and filtering sediment without generating an environmentally dangerous waste trail. The cleaning solution comprises microorganisms of the genus Achromobacter, Actinobacter, Hlcaligene; Arthrobacter, Bacillus, Nocardia, Flavobacterinm, Pseudoinonas and mixtures thereof.
U.S. Pat. No. 6,652,752 discloses method for the biodegradation of an oil-based sludge comprising a mixture of petroleum hydrocarbons. The method comprises forming an aqueous solution in a reactor of an oil-in-water emulsion of the oil-based sludge, bacterial culture and nutrients for the bacterial culture, the bacterial culture having the ability to grow on petroleum hydrocarbons as sole carbon source and having been isolated from a hydrocarbon contaminated soil or hydrocarbon-containing sludge or other environments rich in hydrocarbon degrading bacteria, maintaining the aqueous solution under aerobic conditions in the reactor at a temperature of at least 10° C. for a period of time sufficient to reduce the amount of hydrocarbon by at least 25%, and discharging aqueous solution having a reduced amount of hydrocarbons from the reactor.
The United States Patent Application 20020187545 discloses a process for bioremediation of hydrocarbon-contaminated waste using corn material. The hydrocarbonaceous contaminant is contacted with the corn material in the presence of nutrients and bacteria effective for bioremediation.
The present invention teaches the art to decontaminate efficiently the oil-contaminated soil having soil with free flowing water over it or in soil-water slurry form and the hydrocarbon is either adsorbed in soil/gravel particles or present in the water-soil interface employing a blend of novel microbes.